Landbird monitoring in the Chihuahuan Desert Network: 2016 annual report

Ali, Moez; Bonebrake, Kristen; Valentine-Darby, Patricia; Lien, Lauren

In 2016, landbirds were surveyed within all of the Chihuahuan Desert Inventory & Monitoring Network (CHDN) parks. Sample points were located along a transect for linear features (e.g., most riparian habitats) or a grid for areal features. Seventy-one unique transects or grids were surveyed in 2016. Survey efforts were focused on the breeding season, when increased territorial behavior by songbirds results in higher detection rates and greater sampling efficiency. The window of primary breeding, and therefore sampling, was from April through May, with adjustments made for individual park visits based on latitude and elevation. We used point-transect surveys to estimate and monitor landbird population parameters. Surveys were generally conducted once for each transect or grid when there was ample area to survey. For Carlsbad Caverns National Park (NP), there was only enough habitat to establish one riparian transect, so we surveyed the transect two times on different days to increase sample size. The riparian transect at Guadalupe Mountains NP was not surveyed in 2016, because it was affected by a wildfire that closed off McKittrick Canyon. We also surveyed the grid at Fort Davis National Historic Site (NHS) twice, due to the small size of the park. We conducted a total of 883 point counts on 71 transects or grids. Of these, 755 point counts were conducted in grassland habitat and 128 were conducted in riparian habitat. We recorded a total of 9,162 birds of 134 species during our point counts. Big Bend NP had the highest number of birds counted (n = 2,841), while Fort Davis NHS had the lowest number of birds counted (n = 451). Although species richness and community composition will be estimated in our synthesis reports, observations suggest that these estimates varied widely among the parks surveyed. We observed the greatest number of species at Big Bend NP (n = 90), and the fewest at Fort Davis NHS (n = 35). The number of birds or species counted is influenced not only by the number of points and visits, but also by the size and diversity of available habitats. Black-throated Sparrow was the species counted in the highest numbers within the CHDN (n = 1,215), followed by Northern Mockingbird (n = 711), Cactus Wren (n = 588), and Scaled Quail (n = 451). Ten species (i.e., Black-throated Sparrow, Cactus Wren, Greater Roadrunner, House Finch, Lesser Goldfinch, Mourning Dove, Northern Mockingbird, Pyrrhuloxia, Summer Tanager, and White-winged Dove) were observed at all parks surveyed. Six of the ten species were also recorded at all of the parks in 2014. New species, previously unverified in a given park, were not recorded for any of the parks in 2016.

Landbird monitoring in the Chihuahuan Desert Network: 2016 annual report

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